The first global macrogenetic map of the species that make up marine habitats has been published

Now, a study published in the journal Global Ecology and Biogeography warns that even in marine protected areas (MPAs), the genetic diversity of structural species is not protected, despite the fact that it is essential for the response and adaptation of populations to changes that alter the natural environment.

The work has been prepared by Laura Figuerola-Ferrando, Cristina Linares, Ignasi Montero-Serra and Marta Pagès-Escolà, from the Faculty of Biology of the University of Barcelona and the Biodiversity Research Institute of the UB (IRBio) ; Jean-Baptiste Ledoux and Aldo Barreiro, from the Interdisciplinary Center for Marine and Environmental Research (CIIMAR) in Portugal, and Joaquim Garrabou, from the Institute of Marine Sciences (ICM-CSIC).

Traditionally, marine biodiversity management and conservation plans have considered factors such as species richness. Genetic diversity—another main component of biodiversity—reflects the genetic variety that exists between organisms of the same species and is decisive in the adaptive capacity of populations and their survival. Despite its importance, genetic diversity has so far been overlooked in management and conservation plans.

"Genetic diversity plays a key role in enhancing the capacity of species, populations and communities to adapt to the rapid environmental changes resulting from climate change, and thus increase their resilience", explains researcher Laura Figuerola-Ferrando, first author of the study and member of the Department of Evolutionary Biology, Ecology and Environmental Sciences of the UB.

"However, until now the vast majority of marine protected areas are implemented based on the presence of various species and habitats, without taking into account their genetic diversity. Another example would be the red list of the International Union for the Conservation of Nature (IUCN), which also does not provide for genetic diversity", he adds.

"In recent years, the need to focus conservation efforts on also protecting genetic diversity has been reinforced. Technological progress in the massive development of different techniques to determine genetic diversity (for example, by using microsatellites or small fragments of DNA), as well as their affordable cost, can help to include genetic diversity in management and conservation plans", explains the researcher from the Department of Evolutionary Biology, Ecology and Environmental Sciences of the UB.

The new study applies macrogenetics techniques to identify general genetic patterns of various marine species at large spatial scales. Specifically, the authors have analyzed data from a global database that contains information on the genetic diversity (based on microsatellites) of more than 9,300 populations of 140 species in different marine regions across the planet.

The results profile a reference scenario of genetic patterns in marine habitat-forming species (corals, macroalgae, marine phanerogams, etc.) of potential interest to improve marine life management and conservation plans.

The Northwest Atlantic Provinces and the Bay of Bengal are the regions where the most genetic diversity has been identified in seascape species. In the Mediterranean, quite high values have also been identified (above the global average). Conversely, the marine provinces with the lowest values of genetic diversity are the Gulf of Guinea and the south-western Atlantic.

The conclusions also indicate a positive correlation between the genetic diversity and the species richness of the species forming marine habitats, both animal and plant. However, the work warns of a worrying result: the network of marine protected areas (MPAs) in the large oceanic ecoregions does not preserve areas where the genetic diversity of the species forming marine habitats is higher.

"What we have seen is that what is not being protected in MPAs is genetic diversity. In the study, the initial hypothesis indicated that within these areas there should be more genetic diversity, but this has not been the case. In fact, on a global scale, we have seen that there are no differences in genetic diversity between inside and outside MPAs", emphasizes Laura Figuerola-Ferrando, who is doing her doctoral thesis under the direction of Cristina Linares (UB) and Joaquim Garrabou ( ICM-CSIC).

The authors have also identified a specific pattern in the distribution of the genetic diversity of species forming marine habitats that differs from the traditional models known so far. "This is a bimodal latitudinal pattern: it is a complex biogeographic model and implies that, if we model how the genetic diversity of these species varies with latitude, we find two peaks in temperate zones and a small decline in genetic diversity in the 'Ecuador', explains ICREA Academia professor and professor Cristina Linares (UB-IRBio), one of the coordinators of the study together with Jean-Baptiste Ledoux (CIIMAR).

This scientific discovery is relevant because, until a few decades ago, it was considered that the distribution of biodiversity on the planet followed a unimodal pattern, that is, it had maximum values at the equator and decreased towards the poles. "This is not always the case, especially in terms of species diversity in marine ecosystems. For example, in the case of benthic species, this pattern is more bimodal than unimodal both in terms of species richness and genetic diversity", explains Cristina Linares.

"In our study, the bimodal latitudinal pattern is influenced by taxonomy: in the model used, we found statistically significant differences between animal species (more genetic diversity) and plants (less genetic diversity). In addition, if we explore the latitudinal pattern while separating animal and plant species, we can appreciate how in animals a bimodal pattern continues to be observed; however, the same cannot be said of plants", adds researcher Jean-Baptiste Ledoux (CIIMAR).

The conclusions of the work remind us of the need to include the genetic diversity of populations in the management and conservation plans for biodiversity on the planet. "The importance of taking genetic diversity into account in biodiversity management and conservation plans has just been reinforced with the Kunming-Montreal Global Biodiversity Framework, within the Convention on Biological Diversity (CBD/COP/15/L25, 2022). In this context, we believe that the baseline in the patterns of genetic diversity in species forming marine habitats defined with our work can be very relevant", points out Jean-Baptiste Ledoux.

"On the other hand, if we look at the taxa studied, we see that the Mediterranean Sea is the marine province in which we have studies of the most different taxa (octocorals, hexacorals, sponges, marine phanerogams and algae). In the North Atlantic there is also quite a variety of taxa, especially marine algae and phanerogams, but also hexacorals, octocorals, bryozoans and sponges. On the other hand, in the south of the Atlantic, studies are mainly focused on algae", concludes the team.